It is known in the prior art to produce a variety of oxygenated derivatives of aliphatically-substituted aromatic compounds by oxidation of the aliphatic substituent(s). For example, mono- and polynuclear aromatic compounds such as benzene, diphenyl, naphthalene, anthracene, phenanthrene, etc., having one or more mono- or bifunctional aliphatic groups, may be partially oxidized to derivatives such as alcohols, aldehydes, ketones, peroxides, etc. Mono- and polycarboxylic aromatic acids are also produced by oxygenation of the corresponding aliphatic substituted aromatic compound.
Oxidation processes of the above type are disclosed in U.S. Pat. No. 2,833,816 and Japanese Laid-Open Patent Application (Kokai) No.1 59-27850, wherein aromatic hydrocarbons containing only C.sub.1-4 alkyl groups and/or halogens substituted thereon are oxidized to corresponding oxygenated derivatives by the liquid-phase reaction of the aromatic hydrocarbon substrate with molecular oxygen in the presence of combination catalyst comprising bromine and a heavy metal oxidation catalyst. In addition, it is known (U.S. Pat. No. 5,053,517) to convert methylpyrazoles containing a variety of substituents to pyrazole carboxylic acids by liquid-phase reaction with molecular oxygen and suitable metal-salt catalysts.
Other prior art oxidation processes and their acid products relate to relatively new substituted phenylpyrazoles, which are useful as intermediates in the production of other derivatives which are herbicidally effective in agronomically important crops. Of particular note are certain substituted 3-aryl-5-substituted pyrazole compounds. Examples of such herbicidal compounds are disclosed in U.S. Pat. No. 5,032,165, wherein the chief characteristic feature in the 3-aryl-5-pyrazole compound is the substitution of an --AR.sup.5 group on the 5-position of the pyrazole radical, wherein A is O or S and R.sup.5 is hydrogen or lower (halo) alkyl. An earlier published counterpart of the U.S. Pat. No. '165 patent is EP Application No. EP 0361114, published Apr. 4, 1990. Another process for preparation of these compounds is disclosed in Japanese application No. 06073015-A.
The substituted 3-aryl-5-AR pyrazole compounds in said U.S. Pat. No. '165 patent and EP '114 application are produced by a multi-step procedure involving: (1) halogenation of a methyl group in the 5 position of a 3-phenyl-5-AR.sup.5 pyrazole substrate to form the corresponding 5-halomethyl compound; (2) reacting the latter with an arylamine and formaldehyde in hexamine (i.e., the Sommelet reaction) followed by acid hydrolysis to substitute a formaldehyde group for the halomethyl radical in the 5-position of the phenyl radical and (3) oxidizing said formaldehyde group to a carboxylic acid radical. The resulting compound is useful as an intermediate to form the final product having on the phenyl ring a 5-ester group by esterification of the 5-COOH group with an alcohol.
Other 3-aryl-5-substituted pyrazole compounds having improved herbicidal efficacy are disclosed in related application Ser. No. 07/763,762, now U.S. Pat. No. 5,281,571, a continuation-in-part of Ser. No. 07/600,031, now abandoned, and in South African Patent No. 6,197 (counterpart of U.S. Ser. No. 07/735,091, now abandoned). In said U.S. Pat. No. '571 patent, the compounds are characterized by having a haloalkyl substituent in the 5-position of the pyrazole group, while in said South African Patent No. 6,197, the 5-position of the pyrazole group is substituted with an alkylsulfonyl radical. The compounds in the foregoing patents are prepared in a multi-step process in order to obtain the benzoic acid radical.
The prior art does not disclose methods for the direct oxidation of aryl compounds having as substituents thereon both alkyl group(s) and, additionally, a carbocyclic or heterocyclic group--as exemplified above, wherein multi-step processes are required to form the precursor aryl acid, which is used to form the final ester.
It is, therefore, an object of this invention to provide novel benzoic acid-carbocyclic and 3-benzoic acid-substituted heterocyclic compounds, e.g., 5[substituted pyrazole]-halo-(un)substituted benzoic acids useful as intermediates or precursors to produce the corresponding ester compounds which are useful herbicidal compounds.
It is a further object of this invention to provide a novel process for the direct oxidation of aryl compounds substituted with alkyl (preferably C.sub.1-4) groups and with carbocyclic or heterocyclic groups to produce the corresponding aryl acid/carbocyclic or heterocyclic compounds.
A particular object of this invention is the provision of novel 5[substituted pyrazol]-halo-substituted benzoic acids and a method for the direct oxidation of the corresponding alkyl-substituted precursor compound.
A special object of this invention is to provide the novel compound 5-[4-bromo-1-methyl-5-(trifluoromethyl)-1H -pyrazol-3-yl)-2-chloro-4-fluorobenzoic acid and its synthesis by direct oxidation of the corresponding alkylphenylpyrazole. Esters of said benzoic acid, especially the isopropyl ester, are also provided by esterification of said acid.